The 3 Comma Rules You Need to Know for the SAT/ACT

Bonus Material: PrepMaven’s Comma Rules Worksheet with FREE Practice Questions

Punctuation is one of the biggest English grammar categories tested on both the ACT and the SAT.

In this post, we take a deep dive into one of the most common types of punctuation that appear on ACT English and SAT Reading and Writing: commas.

We’ve already discussed the rules for using commas when it comes down to combining incomplete and/or complete sentences.

But there are 3 more comma rules to cover, which we discuss in this post.

We also give you a chance to apply these rules in practice with our free Comma Rules Worksheet, which includes practice questions, guided examples from official practice tests, and answers/explanations.

Grab it below.

Here’s what we cover in this post:

ACT/SAT Comma Questions in a Nutshell

Students will encounter punctuation questions on the following sections of both tests:

  • ACT English
  • SAT Reading and Writing

Remember: punctuation is one of the most heavily tested English grammar concepts on either test. Students can encounter as many as 18 punctuation questions on ACT English (out of 75 questions) or 7 on the SAT (out of 44 questions).

Punctuation Questions on the ACTPunctuation Questions on the SAT

In general, ACT and SAT punctuation questions boil down to two things: combining sentences and comma rules. 

So if you haven’t done so already, please check out our foundational posts on Identifying Complete and Incomplete Sentences and Combining Sentences

Comma rules won’t necessarily be tested in every SAT or ACT punctuation question. Yet knowledge of comma rules can be vital for nearly all punctuation questions, as the ACT and SAT both love to include commas in incorrect (as well as correct!) answer choices. 

How can you tell that you’re dealing with an ACT or SAT punctuation question?

The answer choices hold the key. A typical punctuation question will have different types of punctuation in the answer choices, including any of the following:

  • Semicolons
  • Colons
  • Periods
  • Commas
  • Long Dashes
  • Parentheses (rare)
  • Apostrophes

Take a look at this sample ACT English question to see this in action:

example ACT English question created by PrepMaven, all rights reserved

Our answer choices here include a comma, semicolon, and colon, which indicates that this is a classic punctuation question!

More overt comma rules questions on the SAT or ACT are likely to just have commas in the answer choices, as in this question here:

SAT and ACT Comma Rules Example Question
Source: CollegeBoard Official SAT Practice Test #1

Notice how the key difference in the answer choices here lies in the placement and quantity of the commas. This is a clue that we’re dealing with a straight-up comma rules question.

Review: Comma Rules and Combining Sentences

When it comes to combining sentences, commas can be used in 2 specific ways:

  1. With a FANBOYS conjunction to join 2 complete sentences
  2. By itself to join 1 incomplete and 1 complete sentence

FANBOYS conjunctions: for, and, nor, but, or, yet, so

If you’re a bit foggy on the differences between complete and incomplete sentences, here’s a brief recap.

Complete SentencesIncomplete Sentences


  • subject
  • verb
  • full expression of an idea

Don’t have:

  • subject
  • verb
  • and/or full expression of an idea

We strongly recommend that you hone your ability to identify sentences before you spend serious time digesting comma rules.

For now, here are some examples of 2 complete sentences joined by a comma + FANBOYS conjunction:

Mina wanted to go to Hawaii for spring break, yet she knew she would need the extra time to complete her research project.

The majority of members supported the new law, so it passed quickly.

Please leave your shoes by the door, for my father is very particular when it comes to clean floors.

And here are examples of 1 incomplete sentence and 1 complete sentence linked by just a single comma. 

On the way to the hospital, the taxi driver regaled us with tales of his own mother’s longstanding battle with ovarian cancer.

Although she longed for some time alone, she ended up having to participate in most of the group activities organized for the conference.

Walking near the harbor, Daniel glimpsed white buoys bobbing far out near the horizon line.

The 3 comma rules we’ll be discussing next are in addition to these 2 rules associated with combining sentences. (Yes, that means that, in total, there are only 5 essential comma rules you’ll need to know for the purposes of the ACT or SAT!)

The 3 Comma Rules You Need to Know for the ACT/SAT

There are 3 additional comma rules you’ll need to know for ACT English and SAT Reading and Writing. The good news is that most students are already familiar with these rules, even if they might feel a bit rusty.

In addition to combining sentences, commas:

  1. Separate items in a list (including before the “and”)
  2. Appear after introductory phrases or transition words
  3. Offset non-essential or additional information from the rest of the sentence

We’ll walk through each rule below.

Comma Rule #1: Separate Items in a List

This tends to be the simplest comma rule for students to remember. 

When listing out items, use a comma to separate each item. On the SAT and ACT, you’ll also need a comma before the and that finishes the list, as in this example here:

Before I leave for the holidays, I need to find a babysitter, submit that annual report, and RSVP for the Christmas party.

In this example sentence, the “items in a list” are actually phrases: find a babysitter, submit that annual report, and RSVP for the Christmas party. We use commas to separate them, including before the “and.” 

Comma Rule #2: After Introductory Phrases

A “phrase” is simply a group of words. Phrases are different from clauses, which contain a subject-verb pair (and can be complete or incomplete).

An introductory phrase begins a sentence, often providing context, time or location cues, or transitions, as in the following examples:

In 1938

On the other hand

Beneath the sofa 

If you start a sentence with an introductory phrase or transition word, you need to place a comma after it. 

In 1938, historians were only just starting to comprehend the impact of the changing times.

On the other hand, such precautionary measures are ones we should be taking on a daily basis, not merely in times of crisis.

Beneath the sofa, Lucy found a panoply of forgotten items, including a keyring, dog toy, and grocery receipt.

Comma Rule #3: Offset Non-Essential Information

This is often the more challenging of these 3 comma rules, as it can be tough for students to identify ‘non-essential’ information in a given sentence.

What do we mean by non-essential or additional information in a sentence? Isn’t everything in a sentence technically essential and necessary?

From a grammatical perspective, sentences can contain non-essential information. Yet we define non-essential here as anything not needed to make a sentence complete

Such information often comes in the form of descriptive phrases, which offer additional information or details about the subject. You can think about these phrases as words you could easily separate from the sentence using a pair of parentheses.


Take a look at this example:

Greg and Kevin, the co-founders of PrepMaven, emphasize the importance of character when it comes to college applications.

Can you spot the non-essential information in this sentence? If you guessed “the co-founders of PrepMaven,” you’re absolutely right!

“The co-founders of PrepMaven” is a descriptive phrase that provides more information about the sentence’s subject, “Greg and Kevin.” It is not needed to make the sentence complete. In fact, we could get rid of it and still have a complete sentence!

Greg and Kevin emphasize the importance of character when it comes to college applications.

That’s actually one way you can test if two commas are actually separating a descriptive phrase or non-essential information from the rest of the sentence. Simply cross off that phrase and see if you still have a complete sentence. If yes, you can safely use those 2 commas; if no, you likely don’t need those commas (or they are being used incorrectly).

So, in sum, you can use 2 commas (like tiny parentheses) to separate non-essential information from the rest of the sentence. Here are 3 more example sentences that show this rule in action:

This rule, while valuable, does not seem to get to the heart of the issue.

Many beginning medical practitioners, most of whom work an astounding number of hours each week, aren’t aware of the fact that they may be offering subpar care later on in the day.

My first real mentor, a fly-shop technician in Denver, taught me what it actually meant to wade into a river and wait for a fish to bite.

Ready to apply these 3 comma rules to sample questions? You can find practice questions, guided examples from official tests, and more in this free Comma Rules worksheet.

Strategy for Applying Comma Rules on the ACT/SAT

Once you’ve identified an ACT or SAT punctuation question, follow these steps to efficiently arrive at the correct answer:

  1. Scan the answers and read for full context
  2. Check for incomplete/complete sentences and eliminate accordingly
  3. Apply other comma rules to remaining answers, if applicable
  4. Eliminate rule-breakers

Remember: it’s not uncommon for the SAT or ACT to test all of the comma rules that we’ve discussed in this post in one single question. 

That’s why it’s important to first apply your knowledge of combining sentences to a punctuation question (i.e., identify if the question is asking you to link two ideas together) before you check for comma rules. 

Let’s apply these steps to one of the sample questions from above.

Example 1

SAT and ACT Comma Rules Example Question
Source: CollegeBoard Official SAT Practice Test #1

1. Scan the answers and read for full context

In the answer choices, we see a semicolon, colon, and commas. Context tells us that the underlined portion is part of a list describing the types of individuals collaborating to find a solution to an issue.

2. Check for incomplete/complete sentences and eliminate answers accordingly.

As we’ve identified that this underlined portion is part of a list, we know that we’re dealing with an incomplete sentence, technically. 

Yet that word “list” should trigger an alarm in your brain–remember comma rule #1? Commas separate items in a list!

We can thus cross off anything that doesn’t have a comma in it, which include A and B. (Remember: semicolons can only join 2 complete sentences, and colons must come after a complete sentence.)

3. Apply comma rules and eliminate rule-breakers

No comma rule tells us that we must have a comma after “and,” only before it. We can cross off D. Our correct answer must be C.

Download Our Comma Rules Worksheet

It’s time to apply your knowledge of comma rules to actual test-like practice questions so you can be extra prepared for Test Day. 

You can do this right now by downloading PrepMaven’s Comma Rules Worksheet.

Comma Rules_SAT and ACT Grammar

With this worksheet, you’ll get: 

  • A recap of the comma rules and strategy discussed in this post
  • Guided examples of comma rules questions from official practice tests
  • 10 FREE test-like practice questions with detailed answers/explanations 

Kate_Princeton Tutoring_AuthorBio Kate

Kate is a graduate of Princeton University. Over the last decade, Kate has successfully mentored hundreds of students in all aspects of the college admissions process, including the SAT, ACT, and college application essay.